Especially in casings for fiber-optic equipment there is often the need to change the filter element of an air filter system of the casing without moving fiber-optic cables or pigtails which are connected to fiber-optic jacks provided at a front plane of the casing. Each movement of a fiber-optic cable may change the transmission characteristics of the respective transmission link, especially the attenuation of the link due to a small bending radius. Also, if actions like changing filter elements are carried out by untrained personnel, there is a risk that the fiber-optic connectors received in respective jacks at the front plane are torn out or the cables are treated such that the fibers break, both resulting in a complete loss of signal in the respective transmission link. As the enclosure of a fiber optic equipment is usually kept as small as possible in order to save space, the respective front panel is usually rather small, which results in a correspondingly small space for connecting fibers or cables right in front of the panel, as often the casings of fiber-optic equipment are stacked one over the other in a mounting rack.
Often, the fiber-optic connecting cables are guided essentially horizontally in front of the panel to the right or left of the casing. Further, the air filter systems are often designed such, that the housing for the air filter element can be accessed from the front panel in order to change the filter element. In these embodiments for an air filter system, the ventilation opening of the casing is usually provided in the left or right side wall of the casing, the ventilation opening having a sufficiently large area and also a height that often extends over almost the entire height of the casing or at least over a considerable part of the height thereof. As a result, the air filter element covering the whole ventilation opening and the filter housing accommodating the filter element also extend over this part of the height of the casing. If in front of the air filter system the fiber-optic connecting cables are to be guided to the respective side of the casing or rack, it is, practically impossible in case of known air filter systems to pull the filter housing out from the casing without moving aside the fiber-optic connecting cables, which involves the afore-mentioned risks.
It is desirable in case of these embodiments of casings for fiber-optic equipment including an air cleaning filter system to use a rather small height of the front panel for both guiding fiber-optic connecting cables and accessing the filter system without the risk or with a reduced risk to affect the transmission characteristics of the respective transmission links by moving the cables or even breaking or disconnecting the fibers from the front panel.
It is thus an object of the invention to provide a filter system for cleaning the air of an enclosure to be ventilated, especially for fiber-optic equipment, which is configurable such that only a minimum space in a given direction is required in order to access the filter system for changing the filter element, even if the ventilation opening does not extend in a plane parallel to the given direction. It is a further object of the invention to provide an enclosure including such a filter system.